PTBSS: A high resolution single component aqueous base soluble chemically amplified resist

Abstract

Poly(4-tert-butoxycarbonyloxystyrene-co-sulfur dioxide) PTBSS has been found to act as a sensitive x-ray (λ=1.4 nm) and weakly sensitive deep ultraviolet (λ=248 nm) chemically amplified, aqueous base soluble positive acting resist. Improvements in the lithographic sensitivity can be achieved by optimizing the post-exposure baking (PEB) conditions. For example, increasing the PEB temperature from 115 °C to 145 °C improved the x-ray sensitivity of a 2.6:1 4-tert-butoxycarbonyloxystyrene (TBS): sulfur dioxide (SO2) resist fivefold. A secondary gain in sensitivity was achieved when the PEB time was extended from the standard 2.5 min to 4.0 min. The sensitivity was also shown to be dependent on the time elapsed from exposure to post-exposure bake. Increasing this time from 1 to 30 min increased the required x-ray exposure energy by 60% arylmethyl model compounds of arylmethyl sulfone have provided information on how the deep-UV sensitivity of PTBSS can be improved from a value of 1800 to 200 mJ/cm.2 Additionally, these model compounds were shown to function as effective acid generating and/or dissolution inhibitor species when added to PTBSS.